Abstract: A semi-spherical shoe 1 includes a semi-spherical surface 1A and a flat end face 1B. The semi-spherical surface 1A comprises a sliding contact region 1a which is disposed in sliding contact with a semi-spherical recess 2B formed in a piston 2, and a lead-in 1b which is located above the sliding contact region 1a or disposed toward a top (recess 1C) of the semi-spherical shoe. The lead-in 1b has a diameter D2 which is greater than the diameter D1 of the sliding contact region 1a, thereby allowing a clearance 8 to be produced between lead-in 1b and an opposing portion of the semi-spherical recess 2B in the piston 2. A reservoir of lubricant oil in a space 4 formed between the semi-spherical recess 2B and the recess 1C of the semi-spherical shoe 1 is introduced into the sliding contact region 1a through the clearance 8. A sliding system having an excellent sliding response over the prior art is provided.

Abstract: A semi-spherical shoe 1 includes an end face 1B which is disposed in sliding contact with a swash plate 3 and a semi-spherical surface 1A which is disposed in sliding contact with a semi-spherical recess 2A formed in a piston 2. A spherical recess 1C is formed in the top portion of the semi-spherical surface 1A to define a space 4 which serves as a reservoir of lubricant oil between the spherical recess 1C and the semi-spherical recess 2B. If the volume of the space 4 which serves as a reservoir of lubricant oil is increased, an accumulation of abraded power in the spherical recess 1C which forms the space can be prevented in a favorable manner.

Abstract: A semi-spherical shoe 1 includes a semi-spherical surface 1A and an end face 1B. The semi-spherical surface 1A comprises a sliding contact region 1a which is disposed in sliding contact with a semi-spherical recess 2B formed in a piston 2, and non-sliding contact regions 1b, 1b′ which are not disposed in sliding contact with the semi-spherical recess 2B. The non-sliding contact regions 1b, 1b′ have a surface roughness greater than the surface roughness of the sliding contact region 1a. The non-sliding contact regions 1b, 1b′ function as a lead-in of a lubricant oil to the sliding contact region 1a. As a consequence, there is provided a semi-spherical shoe 1 having an excellent sliding response as compared with a conventional arrangement in which the semi-spherical surface 1A has a uniform surface roughness over the entire region thereof.

Abstract: A semi-spherical shoe 1 has a convex semi-spherical surface 1A which is disposed in sliding contact with a semi-spherical recess 2A formed in a piston 2. The convex semi-spherical surface 1A is defined by a convex surface of a revolving body which is formed when an arc of a circle having a radius of R2 and having a center C offset from the axis L of the semispherical shoe in an direction orthogonal thereto is rotated about the axis L as a center of rotation. A lead-in 1G which is arcuate in section is formed toward the top of the convex semi-spherical surface 1A and maintains a clearance 7 with respect to the semi-spherical recess 2A. A lubricant oil which is stored in a space 4 is smoothly supplied onto a sliding surface 1F through the clearance 7. The invention provides a semi-spherical shoe 1 having a good sliding response and an increased length of useful life.